body{
    background-color: #f2f2f2;
}
.center{
    width: 1200px;
    margin: 0 auto;
}
.fl{
    float:left;
}
.fr{
    float: right;
}
.clear{
    clear: both;
}
.clearfix::after{
    content: "";
    display: block;
    height: 0;
    visibility: hidden;
    clear: both;
}